1. Field of the Disclosed Embodiments
The present invention relates generally to wireless communications and more particularly to a communication apparatus that operates as a multi-standard compatible terminal that transmits and receives signals having different frequencies.
2. Introduction
Operation of current cellular devices in licensed spectrum worldwide is limited to certain bands such as those identified by the International Telecommunications Union (ITU) as International Mobile Telecommunications (IMT) inclusive of IMT-2000 and IMT-Advanced and their evolutions. As a result, devices constrained to operation in these bands cannot benefit from the potential offered by spectrum sharing techniques such as Dynamic spectrum Access (DSA), Cloud Spectrum Services (CSS), Authorized Shared Access (ASA), Licensed Shared Access (LSA) through which licensed, non-IMT spectrum could become available to cellular users and operators on a dynamic basis. Further, current devices do not generally include radios operating in licensed, non-IMT bands, regardless of whether those bands are operated as dynamically shared bands.
International Mobile Telecommunication (IMT) systems are mobile broadband systems including both IMT-2000 (commonly referred to as 3G systems) and IMT-Advanced (commonly referred to as 4G) and their evolutions. IMT systems provide access to a wide range of telecommunication services including advanced mobile services, which are increasingly packet-based. IMT systems support low to high mobility applications and a wide range of data rates in accordance with user and service demands in multiple user environments and have capabilities for high-quality multimedia applications within a wide range of services and platforms. Detailed specifications of IMT-2000 and IMT-Advanced systems and technologies are contained in International Telecommunication Union (ITU) Recommendation ITU-R M.1457 and Recommendation ITU-R M.2012, respectively.
Modern wireless mobile devices, including IMT devices described above, are typically comprised of multiple radios to enable operation in various frequency bands and/or various wireless networks running different technologies. For instance, a smart phone of today typically incorporates radios operating in licensed bands covering 2G (GSM), 2.5G (e.g. GPRS), and 3G (e.g. WCDMA, HSPA, and the like) technologies as well as radios operating in license-exempt bands covering technologies such as WiFi and Bluetooth.
Spectrum below 6 GHz, which is currently the most suitable spectrum for mobile applications, is allocated to a variety of services including the Mobile Service in ITU Radiocommunications Regulations (RR) that defines allocation of each and every frequency band to various Services (e.g., Mobile, Fixed, Broadcasting, and the like) on a regional and/or global basis. Allocations in the United States overlap significantly with those of the RR. However, only a small fraction, less than twenty percent (<20%), of this spectrum is identified for IMT applications in RR. IMT bands are bands allocated to the Mobile Service and specifically identified for operation of IMT systems and devices via relevant footnotes in RR. The rest is being used by other commercial or government applications, part of which is being lightly utilized due to the nature of the applications and services running in these bands. On the other hand, mobile networks are increasingly under bandwidth exhaustion pressures due to the rapid increase of user demand. This has led to formation of certain spectrum sharing concepts whereby cellular networks could temporarily “rent” or “lease” other licensed, non-IMT spectrum to cover capacity needs of their users. As noted above current mobile cellular devices (wireless devices), however, are not designed to take advantage of the opportunity in sharing these licensed, but under-utilized, non-IMT spectrum bands.